The present invention relates to a piston pin with a bore extending through it.
A piston pin, which is the force-transmission link between a piston and a connecting rod, receives bending, elliptical-deformation, and, in specific cross-sections, shearing stresses from the gas and mass forces that engage it, to the extent that both it and its hubs deform elastically. The contact surfaces between the pin and its hubs, although cylindrical when unstressed, bend and tilt, creating local surface-pressure peaks. In conjunction with the tensile force that acts along the circumference of the pin hubs, this stress can exceed the long-term resistance to vibration on the part of the piston material and lead to what are called hub-gap cracks: fatigue cracking in the apex of the hubs. This can only be prevented with low-deformation piston pins, pins, that is, with thick walls. This solution, however, runs counter to the attempt to keep the dimensions of the mechanism driven by the internal-combustion engine as small as possible and its design as simple as possible.